1. Field of the Invention
The present invention relates to a lens tube of a microscope having a plurality of observation ports, and particularly, to optical path switching means to an observation port.
2. Related Background Art
Conventionally, a lens tube of a microscope having a plurality of observation ports is secured to the main body of the microscope through a circular dovetail, and an optical path switching unit for switching optical paths for a light coming from the main body of the microscope is provided above the circular dovetail. The optical path switching unit has a slide member which is supported to be movable by a guide, and this slide member is provided with three through holes for passing the light coming from the main body of the microscope therethrough. A prism is secured to each of the through holes. An operational lever for moving the slide member is secured to this slide member. It is arranged such that this operational lever is operated to switch to three observation ports to cause the light from the main body of the microscope to enter (see Japanese Patent No. 3318014, for example, FIG. 1).
However, the optical path switching unit of the lens tube of a microscope disclosed in Japanese Patent No. 3318014 requires a space for at least five optical paths including a retreat space of optical members only for sliding the slide member in the lateral direction when the optical path is switched to the three observation ports, which disadvantageously results in an increased size of the system.
In consideration of the above problem, an object of the present invention is to provide a lens tube of a microscope having a small-sized optical path switching means.